This invention relates generally to methods and apparatus for separating intermixed solids and liquids, and more specifically relates to methods and apparatus for separating industrial wastes into solid and liquid phases to facilitate the disposal or recycling of each phase.
Three principal methods of disposing of waste matter are disposal within injection wells, disposal within land fills and incineration. In injection well disposal, liquid waste is pumped into relatively porous rock formations which are bounded by relatively non-porous formations such that the liquid within the porous formation is retained within that formation and is restrained from migration into other formations and/or fluid reservoirs. It will be readily appreciated that because the liquid waste is pumped into a rock formation, such as porous limestone, the liquid must be truly liquid, containing little or no particulate matter which would act to occlude the pores within the formation. This then may, in some cases, require that the liquid contain less than roughly one hundred parts per million ("ppm") of solid or particulate matter and may further require that such particulate matter be of less than roughly two-to-five microns in size, dependent upon the porosity of the formation in which the liquid is to be injected.
In land fill disposal, a pit is formed and a liner of either earthen matter, such as clay, or a synthetic material, such as plastic, is placed within the pit to retain all of the matter disposed therein. Environmental concerns and legislation reflecting those concerns requires that only solid matter be disposed of within land fills so as to avoid any leakage of contaminated waste should a break or tear occur within the liner. A conventional technique of preparing waste containing liquid components for disposal is to mix a liquid adsorbing compound such as flyash or portland cement with the waste to adsorb the liquid and render the waste into a safely disposable solid. Obviously, the greater the liquid component within the waste, the more liquid-adsorbing compound which will be required to solidify the waste. This presents two significant problems; first, the cost of the compound, and second, the greater mass of solid waste to be disposed of. Because of the cost and limited volume of the land fill site, any increase in waste volume has a significant impact upon disposal costs. It is not unrealistic to increase the volume of waste to be disposed of by a factor of three by the time a sufficient amount of adsorbent compound has been added to adsorb a significant liquid phase within the waste matter.
In some cases, such as where organic solids are retained within the liquid, separation of the liquid from the solids may facilitate the disposal of the waste solids by incineration. It will be readily appreciated that the liquid content of the solids, as well as the composition of the solids, will be a major factor in the feasibility of disposal of the waste matter by incineration.
Accordingly, the present invention provides method and apparatus whereby solid and liquid waste products may be substantially separated from one another with a minimal increase in volume of disposable waste.